The bill has received stiff opposition from the National Rifle Association as well as members of Congress who favor gun rights over stricter regulation. The Senate version of the bill currently has 21 cosponsors, all Democrats.

The new version of the bill, introduced last month, prohibits the sale, transfer, importation or manufacturing of about 150 named firearms, plus certain rifles, handguns and shotguns fitted for detachable magazines and having at least one military characteristic. It strengthens the 1994 ban by moving from a two-characteristic test for what constitutes an assault weapon to the one-characteristic test. The legislation would also ban the importation of assault weapons and large capacity magazine and magazines that hold more than 10 rounds.

It would grandfather in weapons legally owned on the day of enactment and exempts more than 2,000 specific weapons "used for hunting or sporting purposes."

The hearing will be the second held by full Senate committee dealing with the congressional response to gun violence.